This application relates to a geared turbofan wherein a gear reduction is straddle mounted with supporting bearings positioned both forward and aft of the gear reduction, and wherein overspeed protection is provided.
Gas turbine engines are known and typically include a fan delivering air into a bypass duct as propulsion and into a compressor as core airflow. The air is compressed in the compressor and delivered into a combustion section where it is mixed with fuel and ignited. Products of this combustion pass downstream over turbine rotors driving them to rotate.
Historically, the fan rotor rotated as one with the fan drive turbine. This resulted in compromise in the design as it may be desirable to have the turbine rotate at a higher speed than the fan.
Thus, it has been proposed to include a gear reduction between the fan drive turbine and the fan rotor.
More recently, the assignee of the present application has developed a commercial gas turbine engine wherein a gear reduction is placed between a low pressure compressor and a fan, such that a fan drive turbine drives the low pressure compressor at one speed and drives the fan at a slower speed.
Such commercial engines have supported the gear reduction on two bearings forwardly of the gear reduction.
It has also been proposed to straddle mount a gear reduction. In a straddle mount gear reduction, bearings are placed on a forward side and on an aft side of the gear reduction. Such an arrangement raises challenges in the event of a failure of a component in the drivetrain of the fan.